1. Field of the Invention
This invention relates generally to a method and apparatus for installing a refractory material to a surface, and more particularly to a method and apparatus for installing a refractory material, which has an embedded anchor accessible via a channel, to a surface of a boiler, an industrial furnace, a heat exchanger or other vessel requiring a heat-resistant or abrasion lining.
2. Description of the Related Art
To attach refractory materials to a surface of vessels, such as furnaces, boilers, heat exchangers or other vessels requiring refractory materials, the gas metal arc welding (GMAW) process may be utilized. In North America, the GMAW process is commonly referred to as MIG (metal inert gas) welding; in Europe, the process is termed MAG (metal active gas) welding. “MIG” as used hereafter refers to both the MIG and the MAG GMAW processes. To produce these welds, either MIG spot or MIG spot plug welding techniques may be used.
A “MIG spot weld” is a timed MIG weld in which two metal components in contact are welded together. The MIG spot weld penetrates a top metal component (e.g., an anchor for a refractory material), and in doing so welds the top metal component to a bottom metal component (e.g., a surface, such as an interior surface, or a wall of a vessel).
A “MIG spot plug weld” is a timed spot weld made on a top metal component that has a bore. The top metal component is welded to a bottom component using a MIG spot plug weld. The MIG spot plug weld utilizes an electrode to provide a resulting weld that sufficiently covers the bore in the top metal component and provides sufficient weld penetration to join the top metal component to the bottom metal component. A MIG spot plug weld generally requires less energy than a spot weld because it is not necessary to penetrate two steel components. Furthermore, MIG spot plug welding generally provides welds that are stronger and more consistent than MIG spot welds.
The weld may be made using GMAW spray transfer, GMAW globular transfer or GMAW pulsed transfer. When a spray transfer mode is utilized, a 2-, 3- or 4-component shielding gas mixture is typically used, along with sufficient current and voltage to produce a stream of weld metal or a stream of weld droplets that cascade across an open arc from the electrode to the weld site. When weld droplets are evident, the droplets will be smaller than the diameter of the electrode utilized.
In globular transfer mode, an open arc process is used with a reactive gas, such as Ar or CO2. Globular transfer mode utilizes less current and voltage than in spray transfer mode. The weld droplets generated are typically larger than the electrode diameter, and the globular weld droplet transfer is irregular.
In pulsed transfer mode, the pulse controls the droplet frequency across an electronically modified open arc. A peak weld current and background current are applied. This process enables an open arc mode of weld transfer of minuscule weld drops. This process can further provide controlled open arc weld transfer at considerably less current than with spray transfer mode.
To attach the refractory material to the surface of the vessel, the most common method used by installers is to stud weld or fillet weld threaded studs on the surface of the vessel and attach carbon steel or stainless steel anchors to the studs. The refractory material is attached to the anchors and the anchors are screwed on to the studs. More specifically, the common method used by installers is to stud weld or fillet weld threaded studs on the vessel by placing a metal stud having a machined protrusion tip in the stud gun. The stud is pressed against the surface of the vessel, and when the tip of the stud is in firm contact with the vessel, the stud gun trigger is pulled and a timed current is applied through the small protrusion tip at the end of the stud. The stud weld current melts the protrusion at the end of the stud tip and a high energy arc is generated between the stud and the grounded vessel. As the stud protrusion is melted, with the force applied to the stud gun, the stud is pushed tight against a ceramic shield located at the end of the stud. The ceramic shield assists in maintaining the necessary weld arc gap and also protecting the stud weld from the atmosphere. The timed weld arc melts the tip of the stud and with the manual force applied the stud is welded to the metal surface.
It is therefore desirable to provide a method and apparatus for installing a refractory material to a surface that provides a simplified and streamlined approach for anchoring refractory materials without the inclusion of a stud.
It is further desirable to provide a method and apparatus for installing a refractory material to a surface that provides savings in materials and labor.
It is yet further desirable to provide a method and apparatus for installing an installation material to a surface that enhances reliability and is useful in a variety of industrial applications.
It is still further desirable to provide a method and apparatus for installing a refractory material to a surface that utilizes a portable welding device capable of controlled, timed activity and creating a stronger and more consistent joint between an embedded anchor of the refractory material and the surface.
It is yet further desirable to provide a method and apparatus for installing a refractory material to a surface that is practiced without the use of threaded studs, nuts or torque tubes, thereby reducing material costs and eliminating potential failure points.
It is yet further desirable to provide a method and apparatus for installing a refractory material to a surface that utilizes a welding gun having a straight or linear neck that enables a one-handed installation of the refractory material to the internal surface of the vessel.